Method and apparatus for attenuating sound in a vehicle exhaust system

ABSTRACT

An exhaust system for the discharge of exhaust gases from a vehicle engine includes a resonator. The resonator comprises a resonator body having at least one, and preferably more than one, elongated composite strip. Each composite strip has a center foil which is corrugated to provide alternate ridges and grooves and is sandwiched between two perforated foils to provide a multiplicity of parallel fluid passages between the corrugated foil and the perforated foils. The composite strips are tightly wound about a central axis parallel to the fluid passages. A housing encloses the resonator body and has an inlet at one end of the fluid passages and an outlet at an opposite end of the fluid passages. The exhaust gases flow through the passages causing a break up and tuning of the sound waves in the system.

FIELD OF THE INVENTION

The present invention relates to exhaust systems for motor vehicles and more particularly to a method and apparatus for attenuating sound in a vehicle exhaust system.

BACKGROUND OF THE INVENTION

Typically, exhaust systems in motor vehicles have one or more resonators for attenuating the sound of emitted gases. While resonators in present use have achieved some degree of success, there is a need for improvement particularly at average or usual driving speeds in a range of 30-45 miles per hour, where the decibel level, and spikes in the decibel level, are not desirable.

SUMMARY OF THE INVENTION

In accordance with this invention, a resonator is provided through which exhaust gases are passed. The resonator breaks up and tunes sound waves in the exhaust gases. The resonator comprises a resonator body including at least one composite strip having a center foil which is corrugated to provide alternate ridges and grooves, and two perforated foils. The corrugated center foil is sandwiched between the two perforated foils to provide a multiplicity of parallel fluid passages between the corrugated foil and the perforated foils. The composite strip is tightly wound about a central axis parallel to the fluid passages. A housing encloses the resonator body and has an inlet at one end for admitting the exhaust gases and an outlet at an opposite end for the discharge of the exhaust gases. The resonator body preferably includes two additional composite strips, all of the same construction.

In a preferred embodiment of the invention, an exhaust line is provided having a first tube section transmitting the exhaust gases from the engine to a catalytic converter. The exhaust line has a second tube section transmitting the exhaust gases from the catalytic converter to the resonator. The exhaust line has a third tube section transmitting the exhaust gases from the resonator to a muffler. Further in accordance with this embodiment, a second resonator is provided for receiving exhaust gases from the muffler. This second resonator may be of a more or less conventional design and is provided to reduce the level of sound to a lower decibel rating.

Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description and accompanying drawings, wherein:

FIG. 1 is an elevational view showing an exhaust system of an automotive vehicle, the exhaust system having a catalytic converter, a muffler and two resonators;

FIG. 2 is a side elevational view of one of the resonators, with parts broken away;

FIG. 3 is a sectional view taken on the line 3—3 in FIG. 2;

FIG. 4 is a fragmentary perspective view of a composite strip which forms part of the resonator shown in FIG. 2;

FIG. 5 is a fragmentary elevational view of one of the foils of the composite strip in FIG. 4, showing the foil laid flat; and

FIG. 6 is a diagram illustrating the sound attenuation achieved by the resonator shown in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

Referring now more particularly to the drawings, there is shown an exhaust system 10 of an automotive vehicle 12. The vehicle 12 is powered by an engine 14. Exhaust gases from the engine 14 are piped to an exhaust gas manifold 16. The exhaust gases from the manifold 16 are transmitted to a catalytic converter 18 by a tube section 20 in an exhaust line 22 of the exhaust system 10.

A tube section 24 transmits the exhaust gases from the catalytic converter 18 to a resonator 26.

A tube section 28 transmits the exhaust gases from the resonator 26 to a muffler 30.

A tube section 32 transmits the exhaust gases from the muffler 30 to a second resonator 34.

A tube section 36 from the second resonator 34 discharges the exhaust gases to the atmosphere.

The resonator 26 comprises at least one and preferably three elongated composite strips 40, 42 and 44. The composite strips are identical in construction and each comprises a center foil 46 which is corrugated to provide alternate ridges 48 and grooves 50 extending at right angles to the lengthwise dimension of the corrugated foil 46. The corrugated foil 46 is sandwiched between and secured to two flat foils 52 and 54 to provide a multiplicity of parallel transverse fluid passages 56 between the corrugated foil 46 and the flat foils 52 and 54. Each of the flat foils 52 and 54 is perforated by a plurality of circular holes 58.

Each of the composite strips 40, 42 and 44 is folded and doubled back on itself about a transverse fold line at the midpoint in its length and is tightly and spirally wound about a central axis 60 that extends parallel to the fluid passages 56. The fold lines are indicated respectively at 62, 64 and 66. As seen in FIGS. 3 and 4, the three composite strips overlay one another in a parallel relationship and are wound in the same direction about the central axis 60, staggered from starting points which are equally spaced apart 120°, to provide a tightly and spirally wrapped resonator body or substrate 68.

Preferably the foils 46, 52 and 54 are each made of stainless steel and are about 0.065 millimeters in thickness. Preferably the holes 58 are about 8 millimeters in diameter and are arranged in staggered rows which are parallel to the lengthwise dimension of the foils 52 and 54. Each hole is spaced from the nearest adjacent holes by a distance of about 2 millimeters.

The resonator body 68 extends lengthwise within a tubular housing 70. The housing 70 has an inlet 72 at one end for admitting exhaust gases from the tube section 24. The exhaust gases pass through the fluid passages 56 and exit from the housing through the outlet 74 at the opposite end of the housing. From the outlet 74, the exhaust gases flow into the tube section 28 which transmits the exhaust gases to the muffler 30.

The resonator 34 may be of conventional construction having a perforated tube 76 passing through a housing 78 filled with a glass fiber insulation 80 or other suitable insulating material.

The resonator 26 breaks up the sound waves of exhaust gases passing through the passages 56 thereof. FIG. 6 illustrates a sound wave 82 for gases passing through the exhaust system 10 that has the resonator 26, and also a sound wave 84 for gases passing through an exhaust system which has a conventional resonator in place of the resonator 26, such, for example, as one like the resonator 34. As can readily be seen, sound wave 82 at the usual engine speeds between 2000 and 3000 RPM (approximately 30 to 45 miles per hour of vehicle speed) for the exhaust system 10 of this invention having the resonator 26 is considerably flattened or smoothed when compared with the sound wave 84 in an exhaust system having a conventional resonator in place of the resonator 26. Note the sudden spike in the decibel rating for the sound wave 84, indicated at 86, in the usual engine speed range. Even outside the usual engine speed range, the sound wave 82 is noticeably smoothed by the resonator 26.

An exemplary resonator body or substrate 68 of the type used in this invention as shown in FIGS. 2 and 3 is sold by Emitec Company to be used for cleaning emissions by adding a layer of precious metal to the foils by a suitable washcoat paint. According to this invention, the substrate, without a layer of precious metal, is used as a resonator to break up the standing wave coming from the engine.

The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention. 

1. An exhaust system for the discharge of exhaust gases from a vehicle engine, comprising: a resonator for breaking up and tuning sound waves from the exhaust gases, said resonator comprising a resonator body including at least one elongated composite strip having a center foil which is corrugated to provide alternate ridges and grooves and is sandwiched between two perforated foils to provide a multiplicity of parallel fluid passages between the corrugated foil and the perforated foils, said composite strip being wound about a central axis parallel to said fluid passages, a housing enclosing said resonator body and having an inlet at one end of the fluid passages and an outlet at an opposite end of the fluid passages, and an exhaust line having a tube for transmitting the exhaust gases from the engine to the inlet of the housing for the movement of the exhaust gases through the fluid passages and out through the outlet.
 2. The exhaust system of claim 1, wherein each of the perforated foils has a plurality of holes, each of said holes has a diameter of about 8 millimeters, and the spacing between each of the holes and the nearest adjacent holes is about 2 millimeters.
 3. The exhaust system of claim 1, wherein said composite strip is folded and doubled back on itself about a transverse fold line.
 4. The exhaust system of claim 1, wherein said resonator body includes second and third elongated composite strips of substantially the same construction as the at least one composite strip, each of said composite strips being folded and doubled back on itself about a transverse fold line at a midpoint in its length, said composite strips overlying one another in a parallel relationship and together being tightly and spirally wound about an axis extending parallel to said passages to provide a tightly wrapped resonator body.
 5. The exhaust system of claim 5, wherein each of the perforated foils has plurality of holes, each of said holes has a diameter of about 8 millimeters, and the spacing between each of the holes and the nearest adjacent holes is about 2 millimeters.
 6. The exhaust system of claim 5, wherein each of said foils has a thickness on the order of about 0.065 millimeters.
 7. An exhaust system for the discharge of exhaust gases from a vehicle engine, comprising: a catalytic converter, an exhaust line having a first tube section transmitting the exhaust gases from the engine to the catalytic converter, a resonator for breaking up and tuning sound waves in the exhaust gases, the exhaust line having a second tube section transmitting the exhaust gases from the catalytic converter to the resonator, a muffler, the exhaust line having a third tube section transmitting the exhaust gases from the resonator to the muffler, and the exhaust line having a fourth tube section transmitting the exhaust gases away from the muffler, the resonator comprising a resonator body including at least one elongated composite strip having a center foil which is corrugated to provide alternate ridges and grooves and is sandwiched between two perforated foils to provide a multiplicity of parallel fluid passages between the corrugated foil and the perforated foils, said composite strip being tightly wound about a central axis parallel to said fluid passages, and a housing enclosing said resonator body and having an inlet at one end of the fluid passages to admit the exhaust gases transmitted to the resonator by the second tube section for movement of the exhaust gases through the fluid passages and having an outlet at an opposite end of the fluid passages to discharge the exhaust gases into the third tube section.
 8. The exhaust system of claim 7, wherein each of the perforated foils has a plurality of holes, each of said holes has a diameter of about 8 millimeters, and the spacing between each of the holes and the nearest holes is about 2 millimeters.
 9. The exhaust system of claim 8, wherein said composite strip is folded and doubled back on itself about a transverse fold line.
 10. The exhaust system of claim 7, wherein said resonator body includes second and third elongated composite strips of substantially the same construction as the at least one composite strip, each of said composite strips being folded and doubled back on itself about a transverse fold line at the midpoint in its length, said composite strips overlying one another in a parallel relationship and together being tightly and spirally wound about said central axis.
 11. The exhaust system of claim 10, wherein each of the perforated foils has a plurality of holes, each of said holes has a diameter of about 8 millimeters, and the spacing between each of the holes and the nearest adjacent holes is about 2 millimeters
 12. The exhaust system of claim 11, wherein each of said foils has a thickness on the order of about 0.065 millimeters.
 13. A method of breaking up and tuning sound waves in exhaust gases discharged from a vehicle engine comprising: providing a resonator comprising a resonator body including at least one elongated composite strip having a center foil which is corrugated to provide alternate ridges and grooves and is sandwiched between two perforated foils to provide a multiplicity of parallel fluid passages between the corrugated foil and the perforated foils, said composite strip being wound about a central axis parallel to said fluid passages, and passing the exhaust gases through the fluid passages of the composite strip.
 14. The exhaust system of claim 13, wherein each of the perforated foils has a plurality of holes, each of said holes has a diameter of about 8 millimeters and the spacing between each of the holes and the nearest adjacent holes is about 2 millimeters.
 15. The exhaust system of claim 13, wherein said composite strip is folded and doubled back on itself about a transverse fold line.
 16. The method of claim 13, wherein said resonator body includes second and third elongated composite strips of substantially the same construction as the at least one composite strip, each of said composite strips being folded and doubled back on itself about a transverse fold line at the midpoint in its length, said composite strips overlying one another in a parallel relationship and together being tightly and spirally wound so that the entire resonator body is tightly wrapped about said central axis.
 17. The method of claim 16, further including enclosing the resonator body in a housing, and admitting the exhaust gases into one end of the fluid passages through an inlet in the housing and discharging the exhaust gases from the opposite end of the fluid passages through an outlet in the housing.
 18. The method of claim 17, wherein each of the perforated foils has a plurality of holes, each of said holes has a diameter of about 8 millimeters, and the spacing between each of the holes and every hole next adjacent thereto is on the order of about 2 millimeters.
 19. The method of claim 18, wherein each of said foils has a thickness on the order of about 0.065 millimeters. 